Direct Measurement of Dynamics in Road Bridges Using a Bridge Weigh-In-Motion System


  • Eugene J. OBrien School of Civil, Structural and Environmental Engineering, University College Dublin, Belfield, Dublin 4, Ireland
  • Arturo González School of Civil, Structural and Environmental Engineering, University College Dublin, Belfield, Dublin 4, Ireland
  • Jason Dowling Dept of Civil Engineering, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
  • Aleš Žnidarič Slovenian National Building and Civil Engineering Institute, ZAG, Dimičeva 12, 1000 Ljubljana, Slovenia



bridge, dynamics, Assessment Dynamic Ratio, soft load testing, Vehicle Bridge Interaction, Weigh-in-Motion (WIM)


A method is presented of measuring a bridge’s characteristic allowance for dynamic interaction in the form of Assessment Dynamic Ratio. Using a Bridge Weigh-in-Motion system, measurements were taken at a bridge in Slovenia over 58 days. From the total observed traffic population, 5-axle trucks were extracted and studied. The Bridge Weigh-in-Motion system inferred the static weights of the trucks, giving each measured event’s dynamic increment of load. Theoretical simulations were carried out using a 3-dimensional vehicle model coupled with a bridge plate model, simulating a traffic population similar to the population measured at the site. These theoretical simulations varied those properties of the 5-axle fleet that influence the dynamic response; simulating multiple sets of total (dynamic + static) responses for a single measured static strain response. Extrapolating the results of these theoretical simulations to a 50-year Assessment Dynamic Ratio gives similar results to those obtained by extrapolating the data measured using the Bridge Weigh-in-Motion system. A study of the effect of Bridge Weigh-in-Motion system errors on the predictions of Assessment Dynamic Ratio is conducted, identifying a trend in the Bridge Weigh-in-Motion calculations of maximum static response. The result of this bias is in turn quantified in the context of predicting characteristic maximum total load effect.


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How to Cite

OBrien, E. J., González, A., Dowling, J., & Žnidarič, A. (2013). Direct Measurement of Dynamics in Road Bridges Using a Bridge Weigh-In-Motion System. The Baltic Journal of Road and Bridge Engineering, 8(4), 263-270.